Prosthesis positioning apparatus and method for implanting a prosthesis

ABSTRACT

An apparatus for positioning a prosthesis in a bone includes a body, first and second clamps, a depth gauge and a guide. The first clamp is coupled to the body. The depth gage is coupled to the body and is movable relative thereto generally perpendicular to the shaft of the bone. The second clamp can be selectively engaged with and disengaged from the depth gage. The second clamp is movable with the depth gage and is also moveable in a direction generally parallel to the axis of the bone. The guide is used to determine the proper rotational orientation of the apparatus. The first clamp is then secured to the bone. The second clamp is secured to a trial prosthesis and is engaged with the depth gage as the trial is inserted into the bone. When the proper insertion depth is reached, the second clamp is secured to the depth gage. The joint is then reduced and the range of motion checked. The depth and rotational orientation may be adjusted as needed. The second clamp is released from the trial, the trial is removed and the prosthesis is inserted in the bone and secured to the second clamp.

[0001] This application is a continuation of co-pending application Ser.No. 09/394,557, filed on Sep. 10, 1999.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] The present invention relates to a device for positioning aprosthesis in a bone and a method of implanting a prosthesis.

[0003] Various prostheses are known for replacing all or part of adamaged or diseased joint. For example, prostheses for replacing all ora portion of a damaged or diseased knee, hip and shoulder of a personare well known. Often, the joint is replaced by securing one portion ofthe prosthesis to one bone of the joint and another portion of theprosthesis to another bone.

[0004] When reconstructing damaged or diseased joints with artificialprostheses, it is desirable to position the components of the prosthesissuch that the structure and function of a properly functioning naturaljoint is replicated to the greatest degree possible. This involvesconsideration of several factors. For example, the components of theprosthesis must be inserted such that the patient has the desired limblength after the surgery. It is also desirable that the range of motionof the joint postoperative is, to the extent possible, the same as thatof a healthy joint. Some of the factors relevant to proper placementinclude insertion depth of the prosthesis components into the bone androtational orientation of the prosthesis components.

[0005] The present invention provides an apparatus for positioning aprosthesis in a bone. According to one embodiment of the invention, anapparatus for positioning a prosthesis having a stem in theintermedullary canal of a bone includes a body, a first clamp connectedto the body for engaging the bone, a depth gage connected to the bodyfor determining the depth of the prosthesis stem within theintermedullary canal, and a second clamp connected to the depth gage forengaging the prosthesis. The body may include a projection forstabilizing the apparatus when the first clamp engages the bone. Aplurality of markings may be provided on the depth gage. The apparatusmay include a guide for determining proper rotational orientation of theapparatus relative to the bone. The guide may be selectively secured toand removed from the body. The second clamp may be movable relative tothe first clamp. The depth gage may be movable with respect to the firstclamp and/or the body. The second clamp may be movable relative to thedepth gage. The body may be provided with a channel and the depth gagemay be connected to a base that is movable within the channel. The basemay include a slot and the channel may include a stop for limitingmovement of the base in the channel. The second clamp may be removablefrom the depth gage and may be engaged with the depth gage in at leasttwo orientations. A cam may be provided for adjusting the first clamp.In one embodiment, the first clamp includes a pair of jaws that engagethe shaft of the bone after the soft tissue is removed.

[0006] In another embodiment of the present invention, an apparatus forpositioning a prosthesis having a stem in the intermedullary canal of abone having a shaft includes a body, a first clamp for engaging thebone, the first clamp being coupled to the body, a depth gage fordetermining the depth of insertion of the prosthesis stem in theintermedullary canal, the depth gage being coupled to the body andmoveable relative to the body in a direction generally perpendicular tothe shaft of the bone, and a second clamp for engaging the prosthesis,the second clamp being coupled to the depth gage for movement therewithand being movable relative to the body in a first direction generallyparallel to the shaft of the bone.

[0007] According to another embodiment of the present invention, anapparatus for positioning a prosthesis having a stem in theintermedullary canal of a bone includes first means for selectivelyattaching the apparatus to the bone, second means for determining thedepth of insertion of the prosthesis stem in the intermedullary canal,the second means being coupled to the first means, third means forselectively engaging the prosthesis, the third means being coupled tothe second means, fourth means for permitting movement of the thirdmeans relative to the first means in a first direction, and fifth meansfor permitting movement of the third means relative to the first meansin a second direction. The first means may include a clamp and a cam foroperating the clamp. The second means may include a post, which mayinclude at least one marking. The third means may include a clamp. Thefourth means may include a post and an opening in the third means thatengages the post. The fifth means may include a body moveable within achannel and the third means may be coupled to the body. The apparatusmay also include a stop in the channel for limiting movement of thebody.

[0008] According to another embodiment of the invention, a method ofimplanting a prosthesis having a stem in the intermedullary canal of abone includes the steps of reaming the intermedullary canal toaccommodate at least a portion of the stem, providing an apparatushaving a first clamp, a second clamp, a depth gage and a guide, usingthe guide to establish the proper rotational orientation of theapparatus, securing the first clamp to the bone, securing the secondclamp to the prosthesis, coupling the second clamp to the depth gage,inserting the stem into the intermedullary canal, and reducing thejoint.

[0009] Other features of the present invention will be apparent to thoseskilled in the art from the detailed description of the preferredembodiments and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is an exploded perspective view of an apparatus forpositioning a prosthesis in a bone according to one embodiment of thepresent invention and a humeral prosthesis.

[0011]FIG. 1a is a perspective view of a body and depth gage that arecomponents of the apparatus of FIG. 1.

[0012]FIG. 1b is a side plan view of a depth gage that forms a componentof the apparatus of FIG. 1.

[0013]FIG. 2 is a partial cross-sectional view showing a clamp thatforms a component of the apparatus of FIG. 1 secured to a humeralprosthesis.

[0014]FIG. 3 is a top plan view showing the apparatus of FIG. 1 securedto a prosthesis for use in a left humerus.

[0015]FIG. 4 is a top plan view showing the apparatus of FIG. 1 securedto a prosthesis for use in a right humerus.

[0016]FIG. 5 is a partial cross-sectional, top plan view showing theapparatus of FIG. 1 positioned about a humerus prior to engagement withthe humerus.

[0017]FIG. 6 is a partial cross-sectional, top plan view showing theapparatus of FIG. 1 engaging a humerus with the prosthesis plantedwithin the intermedullary canal of the bone.

[0018]FIG. 7 is a side plan view showing the apparatus of FIG. 1 securedto a humeral prosthesis and a humerus.

[0019]FIG. 8 shows the apparatus of FIG. 1 in use.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020]FIG. 1 is an exploded perspective view of an apparatus forpositioning a prosthesis in a bone according to one embodiment of thepresent invention. The apparatus generally includes a body 10, a firstclamp 20, a depth gauge 30, a guide 40 and a second clamp 50. Body 10generally includes a central portion 11 having a pair of spaced-apartarms 12 extending from each side thereof. Body 10 further includes achannel 13 having a stop 14 (FIG. 1a) in the form of a post extendingacross the width of channel 13. A projection 15 extends below channel13. A bore 16 is formed in body 10 for receiving screw 17 as describedbelow. A pair of washers 17 a and 17 b are provided for securing screw17 to central portion 11 of body 10, as described below. Body 10 may bemade from any of a number of materials suitable for use in the field oforthopaedic surgery.

[0021] First clamp 20 includes a pair of jaws 21 connected to arms 12 bypins 22. This is best shown in FIGS. 5 and 6, wherein the upper arms 12and part of central portion 11 of body 10 have been removed to betterillustrate bore 16, screw 17, washers 17 a and 17 b and pins 22. Eachjaw 21 includes a first end 23 and a second end 24. In the embodimentshown, an opening or slot 25 is formed in each jaw 21 adjacent first end23. Clamp 20 further includes a cam 26 having a threaded bore 27therein. Bore 27 receives screw 17 to operate cam 26, as describedbelow. A pair of pins 28 project from cam 26 and are located withinopenings 25 of jaws 21 as shown. As shown in FIGS. 5 and 6, washer 17 ais located within a recessed area 18 of body 10. Washer 17 b is locatedbetween central portion 11 of body 10 and cam 26. Both washers 17 a and17 b are aligned with bores 16 and 27 such that screw 17 can passthrough bores 16 and 27 and washers 17 a and 17 b.

[0022] Depth gauge 30, in the embodiment shown, includes a post 31 witha plurality of markings 32 thereon. In the embodiment shown, post 31 hasa generally semicircular cross-section transverse to its longitudinalaxis A. Post 31 is connected to a base 33 that rides within channel 13of body 10, as described below. A first opening 34 is located in base 33for receiving guide 40. A second opening 35 (FIGS. 1a and 1 b) islocated in base 33 and receives stop 14 located in channel 13 of body10.

[0023] Guide 40, in the embodiment shown, is a rod configured to matewith opening 34 in base 33 of depth gauge 30. Guide 40 can be secured toand removed from base 33 as desired.

[0024] Second clamp 50 includes a body 51 having a first jaw 52extending therefrom. Body 51 further includes a pair of spaced-apartarms 53 between which is located a second jaw 54. Jaw 54 is secured tobody 51 by a pin 55 so as to be able to pivot with respect to body 51.This is best shown in FIG. 2, where one arm 53 and a portion of jaw 52have been cutaway to show pin 55. A spring 56 is located between jaws 52and 54. Spring 56 biases second jaw 54 into an open direction. Jaws 52and 54 each include a projection 57 on the inner surface thereof. Body51 further includes an opening 58 configured to engage post 31 of depthgauge 30, as described below. A first screw 59 extends into a threadedopening 59 a in body 51 to secure second clamp 50 to depth gauge 30. Asecond screw 59 b extends into a threaded opening 59 c to move secondjaw 54, as described below. Clamp 50 also includes indicia on body 51 inthe form of the letters “R” and “L” to indicated the proper orientationof clamp 50, as described below.

[0025] Prosthesis 60 is shown in FIG. 1 as a humeral implant forreplacing the proximal end of a human humerus. Prosthesis 60 includes astem 61 with an anterior fin 62, a posterior fin 63 and a lateral fin 64extending therefrom. In the embodiment shown, three suture holes 65 areformed in anterior fin 62 and posterior fin 63. A single suture hole 66is formed in lateral fin 64. Prosthesis 60 further includes a connector67 for receiving the head portion of the prosthesis.

[0026] In use, the humeral shaft is prepared by appropriately surfacingthe resected portion of the shaft and reaming the intermedullary canal.The arm is then positioned such that the palm faces anteriorly and theulna is at a substantially 90° angle to the humerus. Guide 40 isinserted in opening 34 and the apparatus is positioned such that guide40 is substantially parallel to the ulna. First clamp 20 is then engagedwith the shaft of the humerus. This is accomplished by rotating screw 17with an appropriate tool so as to drive cam 26 in the posteriordirection. This causes pins 28 to move within openings 25. As thisoccurs, pins 28 bear on the inner surfaces of openings 25. The spacingof pins 28 and the orientation of openings 25 is such that cam 26 causesends 23 of arms 21 to move toward one another. This causes arms 21 topivot about pins 22 and open at ends 24. Once the apparatus is properlypositioned, screw 17 is rotated in the opposite direction to draw cam 26in the anterior direction. This causes ends 23 of jaws 21 to move awayfrom one another, thereby causing jaws 21 to pivot about pins 22 suchthat ends 24 approach each other. In this manner, clamp 20 is secured tothe shaft of the humerus. Guide 40 may then be removed from opening 34.

[0027] Second clamp 50 is then secured to a trial prosthesis. This isaccomplished by first orienting second clamp 50 such that the properindicia, either L for left or R for right, is facing proximally. Screw59 b is then drawn outwardly so that spring 56 will bias jaw 54 awayfrom jaw 52, thereby opening second clamp 50. Second clamp 50 is thenpositioned such that projections 57 are aligned with the center suturehole 65 on anterior fin 62. Screw 59 b is then advanced so as to pusharm 54 forward, thereby causing it to pivot about pin 55 and graspanterior fin 62 such that projections 57 are located within suture hole65.

[0028] The trial is then positioned above the previously reamedintermedullary canal such that stem 61 is aligned therewith and opening58 in body 51 of second clamp 50 is positioned above post 31 of depthgauge 30 so as to be able to engage post 31. Shaft 61 is then insertedinto the intermedullary canal and opening 58 is slid over post 31. Whenthe desired insertion depth is reached, screw 59 is advanced so as tocontact post 31 and secure second clamp 50 to depth gauge 30. Note thatbase 33 of depth gauge 30 can slide back and forth within channel 13until stop 14 engages either end of opening 35. This allowsanterior/posterior positioning of the prosthesis. Note that, in theembodiments shown, the configuration of opening 58 and post 31 are suchthat opening 58 may engage post 31 in two orientations depending onwhether the prosthesis is to be implanted in a right arm or a left arm.Note also that, in the embodiments shown, the trial prosthesis will beoriented with 30° of retroversion if the preceding steps are followed.This is a result of the proper positioning of clamp 20, the orientationand configuration of post 31 and opening 58 and the positioning ofanterior fin 62. In the embodiments shown, anterior fin 62 and posteriorfin 63 are both positioned at approximately a 60° angle relative tolateral fin 64.

[0029] Once the trial is positioned, a trial reduction is performed andthe range of motion is checked. Adjustments to the insertion depth androtational position of the prosthesis may be made as needed. Once theproper insertion depth and rotational orientation are achieved, theposition of second clamp 50 relative to markings 32 on post 31 is noted.Screw 59 is then loosened and second clamp 50 is removed from post 31and the trial prosthesis is removed from the intermedullary canal.Second clamp 50 is then removed from the trial prosthesis and secured tothe middle suture hole 65 on anterior fin 62 of the prosthesis to beimplanted. The prosthesis is then inserted into the intermedullary canaland opening 58 of second clamp 50 is engaged with post 31. Theprosthesis is inserted until second clamp 50 reaches the predeterminedlocation with respect to markings 32 on post 31. Second clamp 50 is thensecured to post 31. The prosthesis is now in the predetermined positionand may be cemented in place. The apparatus can also be used withprostheses approved for cementless fixation. The apparatus is removedafter implantation.

[0030] In an alternative method, the humerus is prepared as describedabove. A trial that includes height indicia that indicate the insertiondepth is then inserted into the intermedullary canal. Once the properdepth is reached the height indicators on the trial are noted. The trialprosthesis is then rotated to establish the proper retroversion. Thehumeral shaft is then notched adjacent the anterior fin to mark theproper retroversion. First clamp 20 is then positioned such that post 31of depth gauge 30 is aligned with the notch. Clamp 20 is then secured tothe shaft of the humerus. Second clamp 50 is then secured to the trialprosthesis and to post 31. Retroversion then may be checked by insertingguide 40 into opening 34 of base 33. If rod 40 is aligned with theforearm as described above, the prosthesis will be automatically at 30°of retroversion. Again, the retroversion can be adjusted as needed. Atrial reduction is then performed and the range of motion checked. Oncesatisfaction orientation of the trial is achieved it is removed and theprosthesis is implanted. This may be done with or without the assistanceof the positioning apparatus.

[0031] Although the present invention has been described in detail, thesame is to be taken by way of example only and not by way of limitation.Numerous changes and modifications may be made to the embodimentsdisclosed without departing from the spirit and scope of the invention.For example, although use of the apparatus has been illustrated inconnection with a shoulder prosthesis, the apparatus, or a slightlymodified version, could be used with other prostheses, such as thoseused in total hip arthroplasty. Also, the predetermined retroversionangle can be changed by altering the relationship between thecomponents. Accordingly, the present invention is to be limited only bythe terms of the claims.

What is claimed is:
 1. An apparatus for positioning a prosthesis havinga stem in an intermedullary canal of a bone, comprising: a body; a firstclamp connected to the body for engaging the bone; a depth gageconnected to the body for determining the depth of the prosthesis stemwithin the intermedullary canal; and a second clamp connected to thedepth gage for engaging the prosthesis.
 2. The apparatus according toclaim 1 , further including a projection on the body for stabilizing theapparatus when the first clamp engages the bone.
 3. The apparatusaccording to claim 1 , further including a guide for determining properrotational orientation of the apparatus relative to the bone.
 4. Theapparatus according to claim 3 , wherein the guide may be selectivelysecured to and removed from the body.
 5. The apparatus according toclaim 1 , wherein the second clamp is movable relative to the firstclamp.
 6. The apparatus according to claim 1 , wherein the depth gage ismovable with respect to the first clamp.
 7. The apparatus according toclaim 1 , wherein the second clamp is movable relative to the depthgage.
 8. The apparatus according to claim 1 , wherein the depth gage ismovable relative to the body.
 9. The apparatus according to claim 8 ,wherein the depth gage is connected to a base, the body includes achannel and the base is movable within the channel.
 10. The apparatusaccording to claim 1 , wherein the second clamp is removable from thedepth gage.
 11. The apparatus according to claim 1 , wherein the secondclamp engages the depth gage in a first orientation for using theapparatus with a bone located on the left side of the body and engagesthe depth gage in a second orientation for using the apparatus with abone located on the right side of the body.
 12. The apparatus accordingto claim 1 , further including a cam for adjusting the first clamp. 13.An apparatus for positioning a prosthesis having a stem in theintermedullary canal of a bone having a shaft, the apparatus comprising:a body; a first clamp for engaging the bone, the first clamp beingcoupled to the body; a depth gage for determining the depth of insertionof the prosthesis stem in the intermedullary canal, the depth gage beingcoupled to the body and moveable relative to the body in a directiongenerally perpendicular to the shaft of the bone; and a second clamp forengaging the prosthesis, the second clamp being coupled to the depthgage for movement therewith and being movable relative to the body in afirst direction generally parallel to the bone shaft.
 14. The apparatusaccording to claim 13 , further including a cam for operating the firstclamp.
 15. The apparatus according to claim 13 , wherein the depth gageis connected to a base, the body includes a channel and the base ismovable within the channel.
 16. The apparatus according to claim 15 ,wherein the base includes a slot and the channel includes a stop forlimiting movement of the base.
 17. The apparatus according to claim 13 ,wherein the depth gage includes a post with at least one marking. 18.The apparatus according to claim 13 , wherein the second clamp may beconnected to the depth gage in at least two orientations.
 19. Theapparatus according to claim 18 , wherein the second clamp may beconnected to the depth gage in one orientation for use with a bone onthe left side of the patient and a second orientation for use with abone on the right side of the patient.
 20. The apparatus according toclaim 13 , further including a projection located on the body forpreventing the apparatus from tilting relative to the bone.